US4485024A - Process for producing a ferrofluid, and a composition thereof - Google Patents

Process for producing a ferrofluid, and a composition thereof Download PDF

Info

Publication number
US4485024A
US4485024A US06/478,876 US47887683A US4485024A US 4485024 A US4485024 A US 4485024A US 47887683 A US47887683 A US 47887683A US 4485024 A US4485024 A US 4485024A
Authority
US
United States
Prior art keywords
fine particles
active agent
ferrofluid
organic solvent
particulate material
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Ceased
Application number
US06/478,876
Other languages
English (en)
Inventor
Kyozaburo Furumura
Shigeki Matsunaga
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
NSK Ltd
Original Assignee
NSK Ltd
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Priority claimed from JP57056654A external-priority patent/JPS58174495A/ja
Priority claimed from JP57214015A external-priority patent/JPS59105093A/ja
Application filed by NSK Ltd filed Critical NSK Ltd
Assigned to NIPPON SEIKO KABUSHIKI KAISHA reassignment NIPPON SEIKO KABUSHIKI KAISHA ASSIGNMENT OF ASSIGNORS INTEREST. Assignors: FURUMURA, KYOZABURO, MATSUNAGA, SHIGEKI
Application granted granted Critical
Publication of US4485024A publication Critical patent/US4485024A/en
Anticipated expiration legal-status Critical
Ceased legal-status Critical Current

Links

Images

Classifications

    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01F—MAGNETS; INDUCTANCES; TRANSFORMERS; SELECTION OF MATERIALS FOR THEIR MAGNETIC PROPERTIES
    • H01F1/00—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties
    • H01F1/44—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties of magnetic liquids, e.g. ferrofluids
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01F—MAGNETS; INDUCTANCES; TRANSFORMERS; SELECTION OF MATERIALS FOR THEIR MAGNETIC PROPERTIES
    • H01F1/00—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties
    • H01F1/44—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties of magnetic liquids, e.g. ferrofluids
    • H01F1/442—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties of magnetic liquids, e.g. ferrofluids the magnetic component being a metal or alloy, e.g. Fe

Definitions

  • This invention relates to a process for producing a ferrofluid, and a composition thereof. More particularly, fine particles of the ferromagnetic materials such as magnetite, ferrite, iron, cobalt alloy, etc. are dispersed stably in one dispersing medium selected out of an oil group, an ester group or an ether group, whereby a ferrofluid composition having a high magnetizing capacity is produced effectively.
  • fine particles of the ferromagnetic materials such as magnetite, ferrite, iron, cobalt alloy, etc.
  • the ferrofluid is a colloidal solution, in which such ferromagnetic fine particles are dispersed stably and uniformly in a preferred dispersing medium.
  • colloidal solution is neither coalesced nor precipitated under the influence of magnetic force, gravity, centrifugal force, etc., so that the ferromagnetic fine particles are not separated from the colloidal solution.
  • the ferrofluid displays a strong magnetic force responsive to magnetic field.
  • ferrofluid has been used as a sealing agent, a damping agent, a lubricant or the like and various industrial circles pay high attention to its unique properties.
  • dispersing mediums can be used for the ferrofluid.
  • it When it is used for a lubricant or a sealing agent in bearing means, it must have good lubricating property, high heat resistance, low volatility, good chemical stability, etc.
  • the oil group such as a mineral oil, a synthetic oil, etc., the ester group and the ether group are most suitable as dispersing mediums for such ferrofluid.
  • each surface of the ferromagnetic fine particles is required to have a lipophilic nature to be well-adapted to the dispersing medium.
  • the stronger magnetic force thereof causes the stronger sealing force. Further, when it is used as a lubricant, the stronger magnetic force thereof is capable of coping with the mechanical agitation caused by an axial rotation of a rotary shaft, thereby the ferrofluid is prevented from splashing or spoiling the surrounding.
  • the strength of magnetization is dependent upon the concentration of the ferromagnetic fine particles contained in the ferrofluid. Accordingly, it is a very important task to obtain the ferrofluid having a higher concentration thereof. However, if the concentration is higher and higher, a gap between adjacent particles becomes slighter and coalesced easily. Accordingly, a highly concentrated ferrofluid cannot be prepared without realizing the optimum dispersion of the ferromagnetic fine particles in a desired dispersing medium.
  • an aqueous suspension of colloidal ferromagnetic oxide is obtained by the wet method.
  • alkali is added to an acid solution including ferrous ion and ferric ion respectively at the ratio of 1:2, and the thus obtained mixture has more than about pH 9.
  • the mixture is matured at a suitable temperature, so that a magnetite colloidal solution is obtained.
  • the surface-active agent containing an unsaturated fatty acid or its salt as a main material is added to the solution. Then, an excessive quantity of the surface-active agent is added to the solution in order to seal completely each surface of the colloidal particles, thereby two molecular adsorption layers are formed.
  • a first monomolecular adsorption layer of the surface-active agent ion displays a lipophilic nature on its surface
  • a second monomolecular adsorption layer displays a hydrophilic nature on its surface.
  • the ferromagnetic fine particles are rapidly coalesced and settled, thereby separation of the solid from the liquid phase becomes difficult.
  • the surface-active agent ions of the second molecular layer are removed and the surfaces of the fine particles become lipophilic. Then, they are treated with dehydration and drying. Finally, those dried fine particles are dispersed in a desired dispersing medium.
  • the ferromagnetic particles become dispersoid of the obtained ferrofluid, but there are many larger particles in diameter. Accordingly, when those ferromagnetic particles are dispersed in a preferred dispersing medium, the larger particles are precipitated, so that it is not possible to obtain a highly-concentrated ferrofluid having a high magnetizing capacity.
  • the surface-active agent is added to the aqueous suspension having an alkali pH and more than an equipotential point of the colloidal particles, under which condition the surfaces of the colloidal particles are of a negative charge.
  • the surface-active agent such as unsaturated fatty acid having a negative charge in the aqueous solution is unsusceptible to adsorb the particles. Accordingly, some unstable particles are susceptible to arise in the dispersing medium.
  • the process for producing a ferrofluid comprises: a step of adding a surface-active agent and an organic solvent having a low boiling point to ferromagnetic fine particles and coating each surface of said fine particles with the surface-active agent; a step of dispersing the thus coated fine particles in said organic solvent, thereby preparing an intermediate; a step of separating some ferromagnetic fine particles having a bad dispersion property from said intermediate, subsequently mixing one dispersing medium selected out of an oil group, an ester group or an ether group with the intermediate, thereby preparing a mixture thereof; and a step of heating said mixture and evaporating said organic solvent.
  • the process for producing a ferrofluid comprising: a step of adding a surface-active agent and an organic solvent having a low boiling point to ferromagnetic fine particles and coating each surface of said fine particles with said surface-active agent; a step of dispersing the thus coated fine particles in said organic solvent, thereby preparing an intermediate; a step of separating some ferromagnetic fine particles having a bad dispersion property from said intermediate, subsequently adding a poly- ⁇ -olefin oil, a saturated fatty acid having more than 18 carbon atoms and an oxidation inhibitor to said intermediate, thereby preparing a mixture thereof; and a step of heating said mixture and evaporating said organic solvent.
  • the process for producing a ferrofluid comprising: a step of adding a surface-active agent and an organic solvent having a low boiling point to ferromagnetic fine particles and coating each surface of said fine particles with said surface-active agent; a step of dispersing the thus coated fine particles in said organic solvent, thereby preparing an intermediate; a step of separating some ferromagnetic fine particles having a bad dispersion property from said intermediate, subsequently heating said intermediate and evaporating said organic solvent; and a step of adding a poly- ⁇ -olefin oil, a saturated fatty acid having more than 18 carbon atoms and an oxidation inhibitor to said ferromagnetic fine particles obtained by the aforesaid steps.
  • this invention based on the aforesaid processes provides a ferrofluid composition
  • a ferrofluid composition comprising: a poly- ⁇ -olefin oil having an oligomer of 25 to 45 carbon atoms as a main ingredient; ferromagnetic fine particles dispersed in the poly- ⁇ -olefin oil by 1 to 20 volume percent, each fine particle having a particle diameter of from 20 to 500 ⁇ ; a first surface-active agent which is an unsaturated fatty acid having more than 10 carbon atoms and adsorpted on the ferromagnetic fine particles; a second surface-active agent which is a saturated fatty acid having more than 18 carbon atoms; and an oxidation inhibitor of from 0.1 to 10 weight percent of the poly- ⁇ -olefin oil.
  • FIG. 1 is a graph showing a molecular-weight distribution of a poly- ⁇ -olefin oil by viscosity grade.
  • FIG. 2 is a graph showing the effect of an oxidation inhibitor upon a poly- ⁇ -olefin oil.
  • the ferromagnetic fine particles to be used in this invention are the magnetite colloid which is obtained by the wet method.
  • the magnetite colloid in which magnetite powders are ball milled in water or organic solvent may be obtained by the wet ball milling method.
  • the ferromagnetic fine particles are obtained by the wet milling method, a preferred amount of the ferromagnetic powders are dispersed in an organic solvent other than water. And, a certain amount of surface-active agent capable of forming the aforesaid monomolecular layer is added to the ferromagnetic powders as obtained above, and subsequently a mixture thereof may be milled more than a few hours in a ball mill. In such a ferrofluid based on the organic solvent, the yield of the produced colloidal fine particles is favorable because no oily matter is formed on the surfaces of the fine particles.
  • magnetite colloid it is also optional to use not only the magnetite colloid, but also other various ferromagnetic oxidants such as manganese ferrite, nickel ferrite, cobalt ferrite or a composite ferrite made of zinc and any one of the aforegoing substances, barium ferrite or the like. Still further, desired ferromagnetic particles may be obtained by the dry method.
  • Each particle diameter of the ferromagnetic particles to be used in this invention is preferably 20 to 500 ⁇ .
  • the lattice constant of the magnetite is about 8 ⁇ unit lattice and is of a reverse spinel structure. Its crystallization consists of more than several unit lattices and the particle diameter of at least more than 20 ⁇ is required.
  • the marginal rate ⁇ of preventing coalescense between individual particles against an attraction therebetween as well as against an attraction between respective dipoles is 10 3 .
  • the marginal rate ⁇ is 10 2 and the saturated magnetization is 400 G in view of safety
  • the upper limit of the desired particle diameter is 500 ⁇ .
  • it is about 100 ⁇ .
  • the concentration of the ferromagnetic fine particles in the ferrofluid is 1 to 20 volume percent, preferably 2 to 10 volume percent.
  • the concentration of the ferromagnetic fine particles is no less than 0.05 g/ml. Then, the concentration by volume percent is more than about 1 percent. However, when the poly- ⁇ -olefin oil based ferrofluid is used as a sealing agent, the most desirable concentration of the fine particles is from 2 to 10 volume percent of the ferrofluid.
  • the process for producing the ferrofluid according to this invention includes a step of producing an intermediate in which a first surface-active agent and an organic solvent having a low boiling point are added to the aforesaid ferromagnetic particles, and the ferromagnetic particles each of which surface is coated by the first surface-active agent are dispersed in the organic solvent.
  • the first surface-active agent may have at least one polar group or more composed of a carboxyl group (--COOH), a hydroxy group (--OH), a sulfo group (--SO 3 H), etc. and have more than 10 carbon atoms.
  • the first surface-active agent having less than 10 carbon atoms is not favorable in a dispersing condition of the fine particles.
  • Such first surface-active agent may be a sodium salt or a potassium salt of the unsaturated fatty acids such as oleic acid ion, linolenic acid ion, erucic ion, etc., or N-(1,2-dicarboxylethyl) or N-stearilsulfosuccinate or the like.
  • the first surface-active agent when the ferromagnetic fine particles are obtained by the wet method as mentioned previously, the first surface-active agent must be added under the condition that pH of the suspension is set to less than an equipotential point of colloidal particles by adding acid thereto.
  • the colloidal particles are iron oxide
  • pH is preferably no more than 7.
  • each surface of the colloidal surfaces becomes a positive charge and the surface-active agent ion is easily adsorptive.
  • the quantity of the surface-active agent may be the quantity capable of forming a monomolecular layer on the surfaces of the colloidal ferromagnetic fine particles in order to prevent from producing an oily matter due to excessive addition of the surface-active agent or producing a hydrophilic colloid due to formation of the two molecular layers.
  • the ferromagnetic fine particles may be obtained by the wet milling method as described previously.
  • hydrophobic (i.e. lipophilic) fine particles having adsorbed ions of the surface-active agent upon their surfaces are dispersed in a suspension and the organic solvent is added thereto.
  • the ferromagnetic fine particles therein are shifted to the organic solvent through agitation.
  • the intermediate in which the ferromagnetic particles are dispersed in the organic solvent can be obtained.
  • a suspension is prepared by adding an organic solvent having a low boiling point to the ferromagnetic particles. Subsequently, the surface-active agent is added to the suspension, thereby the intermediate is obtained. Otherwise, it may be obtained by adding a mixing solution of the surface-active agent and the low boiling point having organic solvent to the ferromagnetic particles.
  • a water content separated from the ferromagnetic particles is discharged as waste water, and a little water content remaining in the organic solvent can be removed by heating and boiling.
  • the suspension is of the water phase, it is not always necessary to add the organic solvent.
  • the hydrophobic ferromagnetic fine particles have been obtained by purifying and drying the aqueous suspension, it is possible to add an organic solvent to such ferromagnetic fine particles and disperse the latter in the former.
  • the step of preparing the intermediate is not always limited to the aforementioned procedure.
  • Such fine particles of the bad dispersion property are removed by a centrifugal separator of e.g. 5,000 to 8,000 G. After that, a desired dispersing medium selected out of the oil group, the ester group or the ether group is added to the intermediate, and a full agitation is conducted, thereby producing a mixture.
  • a centrifugal separator of e.g. 5,000 to 8,000 G.
  • the step of separating some fine particles of the bad dispersion property from the intermediate is carried out twice.
  • the first selection is made when dispersing the ferromagnetic fine particles in the organic solvent.
  • the second selection is the case that such inferior fine particles are separated by a centrifugal separator.
  • the concentration of the ferromagnetic fine particles in the intermediate product is reduced considerably, but the intermediate product is volatile easily.
  • a large quantity of ferromagnetic fine particles can be dispersed in the ferrofluid.
  • the ferrofluid is required to have low volatility. Thus, evaporation by heating will be difficult.
  • the concentration of the fine particles of a good dispersion property becomes lesser.
  • the organic solvent has a small polarity more or less near to any one of the oil, ester group and ether group and has a low boiling point.
  • it may be a paraffin hydrocarbon such as heptane, hexane, pentane, octane, dodecane, etc., an aromatic hydrocarbon such as cyclohexane, toulene, etc., kerosine or the like.
  • a second surface-active agent Basically, it is soluble to any one of the oil, the ester group and the ether group. More specifically, it may be a nonionic surface-active agent, e.g. polyoxyethylenonylphenolether of which hydrophilic-lipophilic balance (HLB) is from 1 to 5. Addition of the second surface-active agent is not always necessary. However, in case the first surface-active agent is not fully adsorbed on the surfaces of some ferromagnetic particles, the nonionic surface-active agent is adsorbed on the surfaces thereof, thereby displaying the effect of increasing the lipophilic nature and decreasing apparent viscosity.
  • HLB hydrophilic-lipophilic balance
  • the nonionic surface-active agent may be an ether group, an alkylphenol group, an ester group, a sorbitan ester group, a multivalent alcohol or a mixture of the above groups.
  • the second surface-active agent is emulsifiable or soluble with the poly- ⁇ -olefin oil, and may be a saturated fatty acid having more than 18 carbon atoms.
  • the poly- ⁇ -olefin oil is synthesized by lubricating liquids having various grades of viscosity.
  • the viscosity grade depends on the quantity of n of the above formula. (Normally, the symbol n, e.g. monomer, trimer, tetramer, etc. is used. It means n times of a low grade ⁇ -olefin prior to polymerization.)
  • the lubricating liquid in the poly- ⁇ -olefin oil consists of from trimer to sexmer. Table 2 shows the viscosity grade of the poly- ⁇ -olefin oil and their ingredients.
  • the ferrofluids of the present invention exhibit properties of stability of extended times at 80° C. Additionally, such high degree of stability is very effective for magnetic disc requiring high dust-proofing property.
  • the ferrofluid When the ferrofluid is used as a sealing agent for a magnetic disc, we have found that the poly- ⁇ -olefin oil having the viscosity grade No. 6 as listed above has excellent properties as a dispersing medium for obtaining such ferrofluid. On the other hand, when the poly- ⁇ -olefin oils having the viscosity grade Nos. 4 and 5 are used as the dispersing medium, evaporation of the ferrofluid becomes larger. Further, when the poly- ⁇ -olefin oils having the viscosity grade Nos. 38 to 43 are used, the ferrofluid may cause high torque and high temperature in rotary means.
  • the poly- ⁇ -olefin oil of the viscosity grade No. 6 comprises mainly a trimer having 30 carbon atoms and a tetramer having 40 carbon atoms.
  • the range of the carbon atoms of the poly- ⁇ -olefin oil to be used for this invention is from 25 to 45 carbon atoms.
  • it comprises mainly a tetramer having 40 carbon atoms.
  • the carboxylic group of the second surfaceactive agent has a property to adsorb strongly each surface of the ferromagnetic particles. Accordingly, unless some fine particles are fully coated by the first surface-active agent, the carboxylic group of the second surface-active agent is adsorbed on the insufficiently coated surfaces of the fine particles, whereby they enhance the lipophilic nature.
  • the range of the carbon atoms of the poly- ⁇ -olefin oil according to this invention is from 25 to 45. Therefore, a higher number of the carbon atoms of the surface-active agent is better. Preferably, it has more than 18 carbon atoms.
  • the saturated fatty acid is superior to the unsaturated fatty acid in view of thermal stability, because the former has no double bond.
  • the oxidation inhibitor may be e.g. a phenol group, an amine group, a thiophosphate or the like that is used generally for inhibiting oxidation of hydrocarbon. To obtain a further effect, a few kinds of oxidation inhibitors may also be added. As seen in FIG. 2, the addition quantity of the oxidation inhibitor may be from 0.1 to 10 weight percent of the poly- ⁇ -olefin oil. If the weight percent is more than 10 percent, the oxidation inhibitor contributes to oxidative reaction of hydrocarbon.
  • FIG. 2 shows the effect of an oxidation inhibitor upon a poly- ⁇ -olefin oil, wherein the former is 4,4'-metylene-bis-2,6-ditert-butylphenol and the latter is P-60 type manufactured by Bray Oil Corporation.
  • the sample was treated at a temperature of 80° C.
  • the degree of oxidation of the poly- ⁇ -olefin oil is indicated by vaporation quantity thereof.
  • the polarity of the oil group, the ester group or the ether group is relatively similar to that of the organic solvent, so that the ferrofluid fine particles are transferred very smoothly during the evaporation process of the organic solvent. Even if the density of the fine particles in any one of the oil group, the ester group or the ether group is higher, they can be dispersed stably and uniformly therein.
  • the aforementioned method is the wet one. Of course, it is available to obtain the ferromagnetic fine particles by the dry method.
  • the poly- ⁇ -olefin oil When the poly- ⁇ -olefin oil is used as a dispersing medium, some ferromagnetic particles having a bad dispersion property are separated from the intermediate. Subsequently, the intermediate may be heated and the organic solvent having a low boiling point may be evaporated. After this procedure, the poly- ⁇ -olefin oil, the second surface-active agent and the oxidation inhibitor are added to the ferromagnetic fine particles.
  • the ferromagnetic fine particles are to be lipophilic and are dispersed in the organic solvent having a low boiling point, thereby the intermediate is obtained.
  • the poly- ⁇ -olefin oil, the second surface-active agent and the oxidation inhibitor are added to the intermediate.
  • a mixture thereof is prepared and evaporated.
  • the intermediate may be heated and the above three materials may be added thereto. Accordingly, a low boiling content of the intermediate is removed, thereby highly concentrated fine particles are dispersed stably in the ferrofluid.
  • the magnetite particles are dispersed in the polybutene. Separate the former from the latter under the centrifugal force of 8000 G for 60 minutes. By this procedure, some solid particles having a bad dispersion property were removed, and the remainder was a very stable ferrofluid.
  • magnetite particles After drying, take out 5 g of magnetite particles, add to it 25 cc of dioctyl adipate and 5 cc of nonionic surface-active agent of polyoxyethylenonylphenolether (HLB 12.8), and mix them. After mixing, re-heat in a vacuum the mixed liquid in order to completely remove a water content in the dispersing medium as well as a water content adsorbed on the magnetite particles.
  • HLB 12.8 polyoxyethylenonylphenolether

Landscapes

  • Engineering & Computer Science (AREA)
  • Power Engineering (AREA)
  • Soft Magnetic Materials (AREA)
  • Lubricants (AREA)
US06/478,876 1982-04-07 1983-03-25 Process for producing a ferrofluid, and a composition thereof Ceased US4485024A (en)

Applications Claiming Priority (4)

Application Number Priority Date Filing Date Title
JP57056654A JPS58174495A (ja) 1982-04-07 1982-04-07 磁性流体の製造方法
JP57-56654 1982-04-07
JP57-214015 1982-12-08
JP57214015A JPS59105093A (ja) 1982-12-08 1982-12-08 磁性流体組成物とその製造方法

Related Child Applications (1)

Application Number Title Priority Date Filing Date
US06/920,226 Reissue USRE32573E (en) 1982-04-07 1986-10-16 Process for producing a ferrofluid, and a composition thereof

Publications (1)

Publication Number Publication Date
US4485024A true US4485024A (en) 1984-11-27

Family

ID=26397615

Family Applications (2)

Application Number Title Priority Date Filing Date
US06/478,876 Ceased US4485024A (en) 1982-04-07 1983-03-25 Process for producing a ferrofluid, and a composition thereof
US06/920,226 Expired - Lifetime USRE32573E (en) 1982-04-07 1986-10-16 Process for producing a ferrofluid, and a composition thereof

Family Applications After (1)

Application Number Title Priority Date Filing Date
US06/920,226 Expired - Lifetime USRE32573E (en) 1982-04-07 1986-10-16 Process for producing a ferrofluid, and a composition thereof

Country Status (2)

Country Link
US (2) US4485024A (enrdf_load_stackoverflow)
DE (1) DE3312565A1 (enrdf_load_stackoverflow)

Cited By (23)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4701276A (en) * 1986-10-31 1987-10-20 Hitachi Metals, Ltd. Super paramagnetic fluids and methods of making super paramagnetic fluids
EP0250236A1 (en) * 1986-06-19 1987-12-23 Ferrofluidics Corporation Low viscosity, electrically conductive ferrofluid composition
US4741850A (en) * 1986-10-31 1988-05-03 Hitachi Metals, Ltd. Super paramagnetic fluids and methods of making super paramagnetic fluids
US4810401A (en) * 1986-06-12 1989-03-07 Basf Aktiengesellschaft Superparamagnetic solid particles
US4855079A (en) * 1986-10-31 1989-08-08 Hitachi Metals, Ltd. Super paramagnetic fluids and methods of making super paramagnetic fluids
EP0328497A1 (en) * 1988-02-08 1989-08-16 SKF Nova AB Superparamagnetic liquid
US5094767A (en) * 1989-10-05 1992-03-10 Basf Aktiengesellschaft Highly viscous magnetic fluids having nonmagnetic particles
US5143637A (en) * 1990-02-20 1992-09-01 Nippon Seiko Kabushiki Kaisha Magnetic fluid composition
US5147573A (en) * 1990-11-26 1992-09-15 Omni Quest Corporation Superparamagnetic liquid colloids
US5563029A (en) * 1995-04-03 1996-10-08 Eastman Kodak Company Molecular grafting to energetically treated polyesters to promote adhesion of gelatin containing layers
US5627147A (en) * 1995-03-25 1997-05-06 Sankyo Seiki Mfg. Co., Ltd. Lubricating fluid composition for dynamic pressure bearing
US5645752A (en) * 1992-10-30 1997-07-08 Lord Corporation Thixotropic magnetorheological materials
US5656196A (en) * 1994-12-15 1997-08-12 Ferrotec Corporation Ferrofluid having improved oxidation resistance
DE19654864A1 (de) * 1996-02-27 1997-08-28 Thomas Dipl Ing Haehndel Magnetofluid mit einer Sättigungsmagnetisierung von 150 bis 450 mT
GB2319023A (en) * 1996-11-08 1998-05-13 Lg Caltex Oil Corp Ferrofluid to combat oil slicks
US5902513A (en) * 1995-03-27 1999-05-11 Taiho Industries Co., Ltd. Magnetic fluid composition
US20030155771A1 (en) * 2002-02-19 2003-08-21 Innovative Technology Licensing, Llc Electrical generator with ferrofluid bearings
US6768230B2 (en) 2002-02-19 2004-07-27 Rockwell Scientific Licensing, Llc Multiple magnet transducer
US6812598B2 (en) 2002-02-19 2004-11-02 Rockwell Scientific Licensing, Llc Multiple magnet transducer with differential magnetic strengths
US20040251750A1 (en) * 2002-02-19 2004-12-16 Rockwell Scientific Licensing, Llc Magnetic transducer with ferrofluid end bearings
KR100572673B1 (ko) * 2003-10-06 2006-04-19 이진규 지용성 페로플루이드, 그의 제조방법 및 용도
US20080045358A1 (en) * 2006-08-21 2008-02-21 Vandelden Jay Adaptive golf ball
CN120137724A (zh) * 2025-04-17 2025-06-13 湖南澳克科姆能源科技有限公司 一种电磁流变铜铝轧制油及其制备方法和应用

Families Citing this family (29)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPH0766886B2 (ja) * 1986-11-11 1995-07-19 日本精工株式会社 導電性磁性流体組成物
DE3709852A1 (de) * 1987-03-24 1988-10-06 Silica Gel Gmbh Adsorptions Te Stabile magnetische fluessigkeitszusammensetzungen und verfahren zu ihrer herstellung und ihre verwendung
FR2624873B1 (fr) * 1987-12-18 1992-01-10 Rhone Poulenc Chimie Particules composites magnetisables a base d'organopolysiloxane reticule, leur procede de preparation et leur application en biologie
US4956113A (en) * 1988-02-16 1990-09-11 Nok Corporation Process for preparing a magnetic fluid
JP2725015B2 (ja) * 1988-03-11 1998-03-09 エヌオーケー株式会社 磁性流体の製造方法
JPH0642414B2 (ja) * 1988-03-11 1994-06-01 日本精工株式会社 導電性磁性流体組成物とその製造方法
WO1990014672A1 (en) * 1989-05-26 1990-11-29 Wyman John E Superparamagnetic fluids and methods of making superparamagnetic fluids
US5064550A (en) * 1989-05-26 1991-11-12 Consolidated Chemical Consulting Co. Superparamagnetic fluids and methods of making superparamagnetic fluids
EP0443840B1 (en) * 1990-02-21 1995-04-19 Toda Kogyo Corp. Superparamagnetic fine particles of iron oxide and magnetic recording media containing said particles
US5240628A (en) * 1990-12-21 1993-08-31 Nok Corporation Process for producing magnetic fluid
US6503414B1 (en) 1992-04-14 2003-01-07 Byelocorp Scientific, Inc. Magnetorheological polishing devices and methods
US5449313A (en) * 1992-04-14 1995-09-12 Byelocorp Scientific, Inc. Magnetorheological polishing devices and methods
ATE157192T1 (de) 1992-04-14 1997-09-15 Byelocorp Scient Inc Magnetorheologische flüssigkeiten und herstellungsverfahrens
WO1994004313A1 (en) * 1992-08-14 1994-03-03 Byelocorp Scientific, Inc. Magnetorheological polishing devices and methods
EP0672294B1 (en) * 1992-10-30 2001-02-28 Lord Corporation Magnetorheological materials utilizing surface-modified particles
US5382373A (en) * 1992-10-30 1995-01-17 Lord Corporation Magnetorheological materials based on alloy particles
CA2147990C (en) * 1992-10-30 2001-02-20 Keith D. Weiss Low viscosity magnetorheological materials
US5578238A (en) * 1992-10-30 1996-11-26 Lord Corporation Magnetorheological materials utilizing surface-modified particles
US5353839A (en) * 1992-11-06 1994-10-11 Byelocorp Scientific, Inc. Magnetorheological valve and devices incorporating magnetorheological elements
CA2163671C (en) * 1993-06-04 2005-10-25 William I. Kordonsky Magnetorheological polishing devices and methods
DE4327826C2 (de) * 1993-08-16 1995-06-08 Ikosta Gmbh Inst Fuer Korrosio Magnetische Flüssigkeit
DE4325386C2 (de) * 1993-07-23 1997-07-10 Polychemie Velten Gmbh pH-neutrale magnetische Flüssigkeit auf Basis einer wäßrigen Trägerflüssigkeit, Verfahren zu ihrer Herstellung sowie Verwendung
US6613721B1 (en) * 1993-12-29 2003-09-02 The Timken Company Colloidal suspensions for use as a lubricant or additive
DE19514515C2 (de) * 1995-04-12 1997-03-20 Dirk Dipl Chem Guenther Magnetisierbare Dispersionen
US5795212A (en) 1995-10-16 1998-08-18 Byelocorp Scientific, Inc. Deterministic magnetorheological finishing
US6132633A (en) 1999-07-01 2000-10-17 Lord Corporation Aqueous magnetorheological material
US6203717B1 (en) 1999-07-01 2001-03-20 Lord Corporation Stable magnetorheological fluids
DE10342381A1 (de) * 2003-09-13 2005-04-21 Saurer Gmbh & Co Kg Ringspinnspindel mit einer Einrichtung zum Dämpfen ihrer Schwingungen
DE102017106505A1 (de) * 2017-03-27 2018-09-27 NK Neuhäuser Kunststoff GmbH Verträglichkeitsvermittler zur Verträglichmachung von Polyolefin-Gemischen, Verfahren zu dessen Herstellung, sowie Verfahren zur Herstellung von Formteilen aus Polyolefin-Gemischen

Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3700595A (en) * 1970-06-15 1972-10-24 Avco Corp Ferrofluid composition
US3843540A (en) * 1972-07-26 1974-10-22 Us Interior Production of magnetic fluids by peptization techniques
US3917538A (en) * 1973-01-17 1975-11-04 Ferrofluidics Corp Ferrofluid compositions and process of making same
US4094804A (en) * 1974-08-19 1978-06-13 Junzo Shimoiizaka Method for preparing a water base magnetic fluid and product
US4315827A (en) * 1979-11-08 1982-02-16 Ferrofluidics Corporation Low-vapor-pressure ferrofluids and method of making same

Family Cites Families (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE1924331A1 (de) * 1969-05-13 1970-11-19 Bosch Gmbh Robert Traenkmittel mit Rizinusoel fuer selbstheilende Kondensatoren
GB1250379A (enrdf_load_stackoverflow) * 1969-08-25 1971-10-20
US3981844A (en) * 1975-06-30 1976-09-21 Ibm Stable emulsion and method for preparation thereof
US4430239A (en) * 1981-10-21 1984-02-07 Ferrofluidics Corporation Ferrofluid composition and method of making and using same
JPH05144579A (ja) * 1991-11-22 1993-06-11 Matsushita Electric Works Ltd 蛍光ランプ点灯装置

Patent Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3700595A (en) * 1970-06-15 1972-10-24 Avco Corp Ferrofluid composition
US3843540A (en) * 1972-07-26 1974-10-22 Us Interior Production of magnetic fluids by peptization techniques
US3917538A (en) * 1973-01-17 1975-11-04 Ferrofluidics Corp Ferrofluid compositions and process of making same
US4094804A (en) * 1974-08-19 1978-06-13 Junzo Shimoiizaka Method for preparing a water base magnetic fluid and product
US4315827A (en) * 1979-11-08 1982-02-16 Ferrofluidics Corporation Low-vapor-pressure ferrofluids and method of making same

Cited By (36)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4810401A (en) * 1986-06-12 1989-03-07 Basf Aktiengesellschaft Superparamagnetic solid particles
EP0250236A1 (en) * 1986-06-19 1987-12-23 Ferrofluidics Corporation Low viscosity, electrically conductive ferrofluid composition
US4701276A (en) * 1986-10-31 1987-10-20 Hitachi Metals, Ltd. Super paramagnetic fluids and methods of making super paramagnetic fluids
US4741850A (en) * 1986-10-31 1988-05-03 Hitachi Metals, Ltd. Super paramagnetic fluids and methods of making super paramagnetic fluids
US4855079A (en) * 1986-10-31 1989-08-08 Hitachi Metals, Ltd. Super paramagnetic fluids and methods of making super paramagnetic fluids
US4938886A (en) * 1988-02-08 1990-07-03 Skf Nova Ab Superparamagnetic liquids and methods of making superparamagnetic liquids
EP0328497A1 (en) * 1988-02-08 1989-08-16 SKF Nova AB Superparamagnetic liquid
US5094767A (en) * 1989-10-05 1992-03-10 Basf Aktiengesellschaft Highly viscous magnetic fluids having nonmagnetic particles
US5143637A (en) * 1990-02-20 1992-09-01 Nippon Seiko Kabushiki Kaisha Magnetic fluid composition
US5147573A (en) * 1990-11-26 1992-09-15 Omni Quest Corporation Superparamagnetic liquid colloids
US5645752A (en) * 1992-10-30 1997-07-08 Lord Corporation Thixotropic magnetorheological materials
US5879580A (en) * 1994-12-15 1999-03-09 Ferrotec Corporation Ferrofluid having improved oxidation resistance
US5656196A (en) * 1994-12-15 1997-08-12 Ferrotec Corporation Ferrofluid having improved oxidation resistance
US5627147A (en) * 1995-03-25 1997-05-06 Sankyo Seiki Mfg. Co., Ltd. Lubricating fluid composition for dynamic pressure bearing
US5902513A (en) * 1995-03-27 1999-05-11 Taiho Industries Co., Ltd. Magnetic fluid composition
US5700577A (en) * 1995-04-03 1997-12-23 Eastman Kodak Company Molecular grafting to energetically treated polyesters to promote adhesion of gelatin-containing layers
US5563029A (en) * 1995-04-03 1996-10-08 Eastman Kodak Company Molecular grafting to energetically treated polyesters to promote adhesion of gelatin containing layers
DE19654864A1 (de) * 1996-02-27 1997-08-28 Thomas Dipl Ing Haehndel Magnetofluid mit einer Sättigungsmagnetisierung von 150 bis 450 mT
GB2319023A (en) * 1996-11-08 1998-05-13 Lg Caltex Oil Corp Ferrofluid to combat oil slicks
US20040251750A1 (en) * 2002-02-19 2004-12-16 Rockwell Scientific Licensing, Llc Magnetic transducer with ferrofluid end bearings
US7288860B2 (en) 2002-02-19 2007-10-30 Teledyne Licensing, Inc. Magnetic transducer with ferrofluid end bearings
US20040155467A1 (en) * 2002-02-19 2004-08-12 Innovative Technology Licensing, Llc Electrical generator with ferrofluid bearings
US6809427B2 (en) 2002-02-19 2004-10-26 Rockwell Scientific Licensing, Llc Electrical generator with ferrofluid bearings
US6812598B2 (en) 2002-02-19 2004-11-02 Rockwell Scientific Licensing, Llc Multiple magnet transducer with differential magnetic strengths
US6812583B2 (en) 2002-02-19 2004-11-02 Rockwell Scientific Licensing, Llc Electrical generator with ferrofluid bearings
US20030155771A1 (en) * 2002-02-19 2003-08-21 Innovative Technology Licensing, Llc Electrical generator with ferrofluid bearings
US6861772B2 (en) 2002-02-19 2005-03-01 Rockwell Scientific Licensing, Llc Multiple magnet system with different magnet properties
USRE41626E1 (en) * 2002-02-19 2010-09-07 Teledyne Licensing, Llc Multiple magnet transducer with differential magnetic strengths
US6768230B2 (en) 2002-02-19 2004-07-27 Rockwell Scientific Licensing, Llc Multiple magnet transducer
KR100572673B1 (ko) * 2003-10-06 2006-04-19 이진규 지용성 페로플루이드, 그의 제조방법 및 용도
US20080045358A1 (en) * 2006-08-21 2008-02-21 Vandelden Jay Adaptive golf ball
US7682265B2 (en) 2006-08-21 2010-03-23 Vandelden Jay Adaptive golf ball
US20100144464A1 (en) * 2006-08-21 2010-06-10 Vandelden Jay Adaptive golf ball
US7976407B2 (en) 2006-08-21 2011-07-12 Vandelden Jay Adaptive golf ball
US8617006B2 (en) 2006-08-21 2013-12-31 Jay VanDelden Adaptive golf ball
CN120137724A (zh) * 2025-04-17 2025-06-13 湖南澳克科姆能源科技有限公司 一种电磁流变铜铝轧制油及其制备方法和应用

Also Published As

Publication number Publication date
DE3312565A1 (de) 1983-10-20
DE3312565C2 (enrdf_load_stackoverflow) 1991-04-25
USRE32573E (en) 1988-01-05

Similar Documents

Publication Publication Date Title
US4485024A (en) Process for producing a ferrofluid, and a composition thereof
US5505880A (en) Magnetorheological Fluid
US5085789A (en) Ferrofluid compositions
US5507967A (en) Electrorheological magnetic fluid and process for producing the same
US4867910A (en) Electrically conductive ferrofluid composition
US5487840A (en) Magnetic fluid composition
JPH0413842B2 (enrdf_load_stackoverflow)
US6068785A (en) Method for manufacturing oil-based ferrofluid
US5135672A (en) Electroconductive magnetic fluid composition and process for producing the same
JPH0226766B2 (enrdf_load_stackoverflow)
JPS63175401A (ja) 低温用磁性流体
JPS63232402A (ja) 導電性磁性流体組成物とその製造方法
JPS63280403A (ja) 導電性磁性流体組成物とその製造方法
RU2056066C1 (ru) Сухой концентрат магнитной жидкости
JPH01315103A (ja) 磁性流体組成物の製造方法
JPS63124402A (ja) フツ素系磁性流体組成物とその製造方法
JPS63131502A (ja) フツ素系磁性流体組成物
JPS58180596A (ja) 合成油を分散媒とする磁性流体の製造方法
KR100203023B1 (ko) 자성유체 제조방법
JPH0230565B2 (enrdf_load_stackoverflow)
KR0144814B1 (ko) 자성유체의 제조방법
JPH0491196A (ja) 磁性流体組成物
JP3341344B2 (ja) 磁性流体の製造方法
JPS63140505A (ja) 磁性流体組成物とその製造方法
KR100203024B1 (ko) 자성유체 제조방법

Legal Events

Date Code Title Description
AS Assignment

Owner name: NIPPON SEIKO KABUSHIKI KAISHA; 3-2, MARUNOUCHI 2-C

Free format text: ASSIGNMENT OF ASSIGNORS INTEREST.;ASSIGNORS:FURUMURA, KYOZABURO;MATSUNAGA, SHIGEKI;REEL/FRAME:004110/0409

Effective date: 19830303

STCF Information on status: patent grant

Free format text: PATENTED CASE

CC Certificate of correction
RF Reissue application filed

Effective date: 19861016

FEPP Fee payment procedure

Free format text: PAYOR NUMBER ASSIGNED (ORIGINAL EVENT CODE: ASPN); ENTITY STATUS OF PATENT OWNER: LARGE ENTITY